Vehicle alerting system

ABSTRACT

Disclosed is a system for alerting persons in vehicles of the presence in their vicinity of vehicles devoted to responding to emergency situations; the former may be passenger automobiles, buses or other means of public transportation, etc. and the latter may be police cars, fire trucks, ambulances or the like. The system comprises a complete radio station installation in each emergency vehicle and a receiver installation in each passenger vehicle, and both installations may utilize much of the radio equipment already found in such vehicles for other purposes. Thus, in the passenger vehicle, the equipment may comprise an adapter operative to override any normal reception of the car radio to provide an audible and/or visible indication, or a separate indicating receiver of minimum complexity, whereas, in the emergency vehicle, the equipment may comprise a separate modem or one multiplexed to equipment ordinarily serving another function. In the preferred form, the emergency vehicle modem includes a coder-transmitter and a receiver-decoder-indicator both multiplexed to the same antenna, and the passenger vehicle receiver is similar to the receiving equipment of the emergency vehicle.

United States Patent [451 June 27, 1972 Barsh et al.

[541 VEHICLE ALERTING SYSTEM [72] Inventors: Max K. Harsh; James N.Edwards, both of Claremont, Calif.

[73] Assignee: Aerojet-General Corporation, El Monte,

Calif.

[22] Filed: May 21,1970

[2i] Appl.No.: 39,493

[56] autism Clted UNITED STATES PATENTS 3,293,600 l2/l966 Giftt ..340/333,233,217 2/l966 Bost ..340/33 3,37l,278 2/l968Gelushiaetal...,..................340/32X ANTENNA s ECTION TRANSNNTTER[57] ABSTRACT Disclosed is a system for alerting persons in vehicles ofthe presence in their vicinity of vehicles devoted to responding toemergency situations; the former may be passenger automobiles, buses orother means of public transportation. etc. and the latter may be policecars, fire trucks, ambulances or the like. The system comprises acomplete radio station installation in each emergency vehicle and areceiver installation in each passenger vehicle, and both installationsmay utilize much of the radio equipment already found in such vehiclesfor other purposes. Thus, in the passenger vehicle, the equipment maycomprise an adapter operative to override any normal reception of thecar radio to provide an audible and/or visible indication, or a separateindicating receiver of minimum complexity, whereas, in the emergencyvehicle, the equipment may comprise a separate modem or one multiplexedto equipment ordinarily serving another function. In the preferred form,the emergency vehicle modem includes a coder-transmitter and areceiver-decoder-indicator both multiplexed to the same antenna, and thepassenger vehicle receiver is similar to the receiving equipment of theemergency vehicle.

10 Clalrm, 4 Drawing Figures 'ANTENNA MuLTlPLEXER l 1 INVICATOR SECTIONPATENTEDJum m2 SHEEI 2W? INVENTORS MAX K. BARSH BY JAMES N.EDWARD5ARTHUR DECKER ATTORNEYS VEHICLE ALERTING SYSTEM BACKGROUND OF THEINVENTION Incident to the ever-increasing use of the highways is theproblem of communications, especially that directed to alerting theoccupants of a moving vehicle to the presence in its vicinity of avehicle in emergency service, which is entitled to pre-empt the use ofthe highway, so that the former may divert to provide a clear path forthe latter. Systems have been proposed: some involve the use of pluralpermanently fixed installations of radio equipment along the roadsides,some involve computer-controlled telephone dial-up facilities, some, inrecognition of the success of manufacturers to insulate the interiors ofcars from outside noise, are responsive only to signals which may beheard in the immediate environs of a car and thus carry externalmicrophones, emergency signal filters and other elaborate electronicdevices, and still other depend upon complex roadway-monitoring centralstations attended by traffic experts, a system with appreciableresemblance to the control towers at airports. Either outright rejectionor considerable delay in the acceptance of the aforementioned systems isexpected mainly because: (a) they all attack a plurality of problemsincident to highway transportation, and (b) they require extensive andcostly equipment installations on all roads used. In contradistinction,the equipment required by the present invention reside within thevehicles and are thus operative whenever the vehicle is operated and,additionally, may employ much of the equipment already in the vehiclefor other purposes.

BRIEF SUMMARY OF THE INVENTION The present invention is devotedparticularly to the need for a warning device installed inside movingvehicles to alert its occupants of the approach and/or proximity ofemergency vehicles. It discriminates from the high incident noise (orsound) level outside or within the vehicle, it operates regardless ofhow well sound-insulated the vehicle may be and it provides a warning ofthe presence of an emergency vehicle despite the overpowering,self-generated warning signals radiated by each.

The invention, in the preferred embodiment to be described here,comprises electronic equipment as follows: in each emergency vehicle, amodem, the transmitter of which is pulse-code modulated and the receiverof which is capable of being inhibited by the transmitter so as to beresponsive only to signals generated outside and, in each passengervehicle, a receiver responsive to any transmitter to energize anindicator.

The present system includes selected different transmitter interpulseperiods with true statistical random tum-on and drift instability.Half-second transmitted pulses at low duty cycle provide randomoccurrence of gated modulation (15 Khz). This format, while nonoptimumfrom the viewpoint of communication efficiency, provides exceptionalcircuit simplicity. The received signal operates a visual indicator andkeys an audible alann signal. In each emergency vehicle, a second visualindicator monitors its transmitter and an inhibit signal cuts off itsreceiver when its transmitter is energized.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a typicalmodem contemplated by the invention for installation in an emergencyvehicle;

FIG. 2 is the detailed block diagram corresponding to FIG.

FIG. 3 contains a set of waveshape graphs depicting the activity of thecomponents of FIGS. 1 and 2; and

FIG. 4 is the schematic diagram of encoder 22 of FIG. I.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. I is shown a sketch ofemergency vehicle I containing modem 12, comprising transmitter section14, receiver section I6, antenna section 18 and indicator section 20.

Transmitter section 14 includes encoder 22, which generates an outputsignal comprising a sequence, each sequence consisting of a series ofpulses at, typically, 15 Khz for a period of one-half second, followedby an interstice of no output for a period of one second. It is pointedout that these rates are nominal only since it is inherent in the systemof this invention that encoder 22 not be drift-free, and, further, thatthe mean duty cycles will be different for different vehicles. Thesignal from encoder 22 is fed to transmitter 24 which operates withinthe authorized radio band at, for instance I50 Khz. This signal is poweramplified to a desired output power level by transmitter 24 and fed, inantenna section 18, to multiplexer 26 and thence to antenna 28. Duringintervals for which antenna 28 is excited, green lamp 32 in indicatorsection 20 is energized via line 30, thereby infonning the operator ofvehicle 10 that an emergency warning signal is being emitted by his ownvehicle.

Any signal from another emergency vehicle in the vicinity is received inantenna section 18 by antenna 28 and directed by multiplexer 26 toreceiver section 16.

In receiver section 16, receiver 34 detects the 150 Mhz carrier andpasses the l5 Khz modulation to decoder 36 which filters, detects andamplifies it to energize a pair of alarms at indicator 20:via line 38,red lamp 40 and, via line 42, loudspeaker 44 with a 3 Khz audible tonefrom a local oscillator keyed on by the detection of the signal.

Reference is now made to the detailed block diagram cor responding tothe system of the invention presented in FIG. 2 and the waveshapesindicative of its operation given in FIG. 3.

Encoder 22 of transmitter section 14 employs flip-flop $0, controlled bycharging circuit 52, to provide, during about the initial half-second ofevery IV: second period, a relatively high voltage level on line 54,which leads to line 30 and to 15 Khz, free-running, square-waveoscillator 56; this activity is shown by curve A in FIG. 3. It has beenpointed out that no provision is made to control drift i.e.,non-synchronous operation of encoder 22; thus, curve A shows first pulse58 in synchronism but second pulse 60 with a leading edge somewhat earlyand a trailing edge later, and third pulse 62 with a leading edgesomewhat late. As a result, oscillator 56 is gated on during the pulseperiods, as shown by curve B.

A schematic diagram appropriate for encoder 22 is presented in FIG. 4,in which it is seen that, when output 64 of flip-flop 50 switches to ahigh voltage level, charging circuit 52 excites the emitter oftransistor 68 to trigger input 70 of flipflop 50 so that output 72 is ata high voltage level (waveshape A, FIG. 3). This, of course, drivestransistor 74 which excites line 30, thereby cutting off receiversection 34 and energizing lamp 32 (green) in indicator section 20, andalso causes oscillator 56 to generate a l5 Khz squarewave (waveshape B,FIG. 3) on line 74 to transmitter 24.

Returning to FIG. 2, transmitter 24 comprises oscillator 76, typicallyoperating at 50 Mhz, the output of which is multiplied by tripler 78 tol50 Mhz and then fed to modulator 80 in which it is modulated bywaveshape B to provide waveshape C on line 82. This signal is fed tomultiplexer 26 (a transmitreceive switch or multicoupler) and to antenna28.

Any incoming signal (waveshape D, FIG. 3) from another emergency vehicleis fed through antenna 28 and multiplexer 26 to receiver 34, whichincludes detector 84 or, optionally, input amplifier and filter.Detector 84, which is active only if line 30 is carrying no signal fromencoder 22, removes the signal carrier (150 Mhz) to form waveshape E(FIG. 3). This is filtered in decoder 36 by 15 Khz narrow band filter 86and then further demodulated by detector 88 to remove the IS Khz portionand give waveshape F, on line 90, which feeds indicator section 20.

In indicator section 20, line 90 branches to lines 38 and 42, the formerof which excites red lamp 40, thereby indicating that a signal is beingreceived from another emergency vehicle, and the latter of which excitesoscillator 92. Oscillator 92 comprises a 3 Khz generator which drivesloudspeaker 44; thus, the presence of an emergency vehicle is indicatedvisually by red lamp 40 and aurally by loudspeaker 44.

It is appreciated that the above description has contemplated equipmentas incorporated in an emergency vehicle, whereas the invention isdirected to a system which contemplates equipment in ordinary passengervehicles also. It should be apparent that the latter may comprise onlyantenna, receiver and indicator sections 18, 16 and 20, respectively,the first of which need not be provided with multiplexer 26, the secondof which may omit the inhibit connection to detector 84 and the last ofwhich may omit green lamp 32.

It should also be pointed out that the system of the invention mayprovide an indication of an emergency to pedestrians or to vehicles theemergency equipment of which are inactive or this may be accomplishedsimply by the addition in other receiving vehicles of indicators (suchas lamp and/or loudspeaker 44) which would be apparent in the vicinity.

Further, in order not to encumber the description, portions of optionalequipment have not been treated; thus, intensity and volume controls,power amplifiers, etc. are omitted. The necessity for these is felt tobe a function of ordinary engineerin g decisions and their design isconsidered a result of skill-ofthe-art effort.

What is claimed is:

l. in an alarm system for emergency vehicles, a plurality of transmittersections, each said transmitter section comprising:

an antenna;

a transmitter connected to excite said antenna;

signal generating encoder means for modulating said transmitter, saidencoder means having a different duty cycle than, and being adapted tooperate in non-synchronism with respect to the signal generating encodermeans of any other transmitter section in said system.

2. The system of claim 1 wherein said encoders operate at different dutycycles.

3. The system of claim I and an indicator responsive to said encoder toindicate excitation of said transmitter and antenna.

4v The system of claim 1 and a receiver section responsive to thesignals from the transmitter sections of other vehicles.

5. The system oi'claim 4 and an indicator responsive to excitation ofsaid receiver section.

6. The system of claim 4 and means to cut off response to said receiversection during operation of said encoder.

7. The system of claim 4 and a multiplexer operative to provideselective operation of said antenna by said transmitter and saidreceiver section.

8. The system of claim 5 wherein said indicator operates both visual andaural outputs.

9. The system of claim 5 and second means also responsive to excitationof said receiver section to indicate outside of the vehicle.

10. An alarm system for a substantially enclosed area such as a vehicle,capable of indicating the presence of an emergency, adapted for use in afleet comprising both emergency and receiving vehicles, said systemcomprising:

in the receiving vehicle,

an antenna,

a receiver,

a decoder and an indicator; and

in each emergency vehicle,

an antenna,

a transmitter,

a signal generating encoder means for modulating said transmitter, saidencoder means having a different duty cycle than, and being adapted tooperate in nonsynchronism with respect to, the signal generating encodermeans of any other transmitter section in any other emergency vehicle,

a receiver,

adecoder, means to inhibit operation of said emergency vehicle receiverwhen said emergency vehicle encoder is operated and means to multiplexsaid emergency vehicle antenna between said emergency vehicletransmitter and receiver.

l l II

1. In an alarm system for emergency vehicles, a plurality of transmittersections, each said transmitter section comprising: an antenna; atransmitter connected to excite said antenna; signal generating encodermeans for modulating said transmitter, said encoder means having adifferent duty cycle than, and being adapted to operate innon-synchronism with respect to the signal generating encoder means ofany other transmitter section in said system.
 2. The system of claim 1wherein said encoders operate at different duty cycles.
 3. The system ofclaim 1 and an indicator responsive to said encoder to indicateexcitation of said transmitter and antenna.
 4. The system of claim 1 anda receiver section responsive to the signals from the transmitterseCtions of other vehicles.
 5. The system of claim 4 and an indicatorresponsive to excitation of said receiver section.
 6. The system ofclaim 4 and means to cut off response to said receiver section duringoperation of said encoder.
 7. The system of claim 4 and a multiplexeroperative to provide selective operation of said antenna by saidtransmitter and said receiver section.
 8. The system of claim 5 whereinsaid indicator operates both visual and aural outputs.
 9. The system ofclaim 5 and second means also responsive to excitation of said receiversection to indicate outside of the vehicle.
 10. An alarm system for asubstantially enclosed area such as a vehicle, capable of indicating thepresence of an emergency, adapted for use in a fleet comprising bothemergency and receiving vehicles, said system comprising: in thereceiving vehicle, an antenna, a receiver, a decoder and an indicator;and in each emergency vehicle, an antenna, a transmitter, a signalgenerating encoder means for modulating said transmitter, said encodermeans having a different duty cycle than, and being adapted to operatein non-synchronism with respect to, the signal generating encoder meansof any other transmitter section in any other emergency vehicle, areceiver, a decoder, means to inhibit operation of said emergencyvehicle receiver when said emergency vehicle encoder is operated andmeans to multiplex said emergency vehicle antenna between said emergencyvehicle transmitter and receiver.